Shades Of Green
by ThePossibilityOfMagic
Summary: Kate Beckett had never been the jealous type; but then, Richard Castle had a habit of changing things.


_Because everybody loves a little jealous Beckett. :) _

_I'm pretty sure this one was inspired by Kate and Ali (Kate-hi and Castle41319 on Tumblr) because they both seemed to be having a bad day at the time, and when people on Tumblr are having bad days my immediate response is to start writing some silly Castle fanfiction... :) Unfortunately, this is probably coming about a month too late... but ah well, better late than never._

_Disclaimer: Jealous Beckett (or any other form thereof), like every other Castle character, belongs to Andrew Marlowe and his team, not me._

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><p>"Okay, seriously, what the <em>hell<em> was that?"

Caught off guard by his partner's sudden outburst, Castle slowed his stride, throwing a quick glance back towards the bathroom door before eyeing her warily, alarm bells already ringing loudly in his ears.

"Beckett, I'm sorry, but when you gotta go–"

Beckett shot him a vexed look, her arms folding tightly across her chest.

"God, Castle," she bit out, "I'm not talking about your bathroom habits, I'm talking about that little display upstairs. We were _supposed_ to be here to talk to the manager, and yet when I get into the office and start to introduce us, you're nowhere to be found– all because you're still back at the desk, chatting up the goddamn _receptionist_!"

"W- We were just talking, that's all," Castle squeaked, his eyes wide in the face of such unexpected ire. Beckett rarely lost her temper, and almost _never_ at him; whatever he had done, it was bad.

"Uh-huh," Beckett retorted, her expression scornful. "That's why you were slipping her your number, right? Because you wanted to _just talk_ some more?"

Castle blinked, faltering. "That was just– well, that was– seriously, Beckett, it's not what you think. I swear. Just let me explain–"

Then, as another piece suddenly clicked into place, he suddenly broke off, his eyes fixing on hers, wide and questioning.

"Wait, is this why you were so quiet in the elevator?"

Ignoring his question, Beckett stepped in closer, a finger jabbing at his chest. "She's half your age, Castle! Just because she's young and beautiful–"

Castle caught her hand before she could poke him again, his other hand lifting in a gesture of surrender as he interrupted her.

"Beckett, wait. Stop," he implored her, "You don't understand. There's no need to get mad–"

"I'm not mad!"

Feeling his body tensing with frustration– an emotion evoked partially by her irrationality, but mostly from yet again having to suppress the near-uncontrollable urge to shove her against the wall and kiss her senseless– he tugged on the hand that he still held captive, pulling her in even closer.

"Really?" he shot back, eyebrows raised in challenge. He was goading her, pushing her buttons, and he knew it– just as he knew he wasn't stopping now. Then, his voice dry and edged with just a hint of sarcasm, he went on, "Because the shouting kind of suggests otherwise. So how about you stop glaring and throwing accusations in my face for a minute and actually tell me _why_ you're so pissed with me for _talking_ to someone!"

"Because you're _mine!_" she burst out furiously, then froze, blinked, and quickly backpedaled, amending hastily, "My _partner._ You're my partner, which means you're supposed to always have my back, not be MIA as soon as some young bimbo catches your attention!"

Completely taken aback, Castle simply stared at her in wordless shock, his head spinning, her words echoing loudly in his ears.

_You're mine._

###

The silence was deafening.

Breathing hard, Beckett continued to meet his gaze, somehow unable to look away. Part of her wanted to run, to turn and dash for the exit, and to keep running until she could no longer feel the burn of his eyes on her, the piercing gaze that seemed to be seeing far deeper than she'd ever meant anyone to see.

And all because she'd let it get to her; let the idiotic little voice at the back of her mind take over, blinding her to everything except the image of him leaning on the receptionist's desk, smiling down at the beautiful, large-chested young woman who was looking back at him like he was some kind of real-life Prince Charming come to take her to the ball.

_Stupid, stupid, stupid._

There was going to be no easy recovery from this, no way to shove that particular feline back into its bag. All she could hope for was that he would choose to be merciful, to let the whole thing blow over and move on as if nothing had ever happened.

Which, from the way he was still staring at her– open-mouthed, wide-eyed and speechless– seemed like it would prove to be a vain hope.

Watching him warily, she held her breath, waiting for the tsunami that would surely follow the earthquake she'd just created, shaking them both to their core. She was just considering saying something to try and gloss it over somehow– exactly what she would say, she had no idea– when suddenly, to her surprise and confusion, his expression shifted, his mouth twitching almost imperceptibly, the muscles tightening as though he were trying to hide a smile.

"You're right," he answered slowly, eyeing her in that intent way that he always did when she got too close to revealing too much. "You're my partner, and I'm yours. I'm sorry."

Then, with just the tiniest hint of mischief playing in his eyes, he added, "And I promise, yours is the only back I'm interested in watching."

Sensing both his teasing and the more serious subtext beneath it, Beckett narrowed her eyes at him, determinedly ignoring the suddenly unsteady rhythm of her heart as she struggled to decipher exactly what had just happened between them. Could he really be letting her admission go so easily? And if so, why did she feel almost... _disappointed?_

Searching his eyes with hers, she suddenly became very aware of just how very close they were standing, and of the fact that his large hand was still wrapped firmly around hers, keeping it anchored tightly against his chest.

She was still trying to remember how to move– breathing and coherent thought would be next on the agenda– when suddenly a soft voice spoke up from behind them, its tone quiet, uncertain.

"Uhm… Mr Castle?"

The moment broken, Beckett blinked and took a hasty step back, seeking sanctuary in distance. Mercifully, Castle relinquished his grip on her hand, but held her gaze for a second longer, his eyes boring deep into hers, before slowly turning to face the newcomer, eyebrows raised.

"Yes?"

The woman– none other than the young receptionist from upstairs, Beckett saw with surprise– swallowed slightly, then blew out a breath, her eyes determined as they fixed on Castle's.

"I'll do it."

Castle gave her a small, approving smile and nod, but Beckett simply frowned, confused. "I'm sorry, do what?"

Again Castle turned to face her, his eyes twinkling and voice deceptively innocent as he informed her, "When we were, ah, _chatting_ before, Lisa here happened to share with me some very interesting information that could just give us the lead we need in this case. As I deemed this information to be of great value to us, I requested that she come to the station so that _my partner and I_ could interview her properly, but she was hesitant to place herself at risk of being caught out by her boss. So, I gave her your number and told her we'd also hang around down here for a little bit in case she changed her mind."

Again seeing the telltale twitch of his lips, Beckett shot him a dark look before turning back toward the young woman, forcing herself to focus.

"Lisa, I want to thank you for doing this, and I promise you, we'll do everything we can to keep you shielded from any kind of repercussions. Your boss never has to know that you talked to us."

Seeing the younger woman bite her lip and give a small nod, Beckett smiled encouragingly.

"How about we give you a ride to the station? We can talk there, where there's no-one to overhear."

Lisa shook her head. "I can't, not now. My boss thinks I'm on my lunch break and I've only got fifteen minutes. He'd notice if I was gone any longer. But I get off work at five, if that's okay?"

Beckett nodded. "That sounds great, Lisa. And thank you."

Leaving the anxious young woman with her number and the precinct's address, Beckett and Castle thanked her again and swiftly headed out of the building, wary of the dangers of being seen talking to the girl.

As they crossed the road to the car, Beckett spoke up, her voice dry.

"You know, you could have said something."

Slowing slightly, Castle lifted his eyebrows. "You might have been a little too busy yelling at me to notice, but I _did_ try."

"Why do I get the feeling you really weren't trying very hard?"

Reaching the car, he grinned at her over the roof. "Now, where would be the fun in that?"

Beckett scowled, her hand grasping the handle of the car door. "You're an ass."

"Granted, but you can't deny that I make a damn good partner."

Rolling her eyes at him, she said nothing– because she couldn't deny it, after all– and stepped into the car, keeping her gaze directed straight ahead as he slid into the passenger seat beside her.

"So…" Castle began, and Beckett clenched her teeth, bracing for the merciless teasing that was surely to come.

She didn't have to wait long. Turning slightly to look at her, Castle smiled, a slow, lazy smile that seemed to have a fibrillatory effect on her heart. "Green becomes you, Detective."

Narrowing her eyes, she glared at the road in front of her, knowing better than to meet that intent blue gaze. "Shut up, Castle."

She could still see him smirking out of the corner of her eye. "I'm just saying –"

"Well, don't."

Seemingly seeing the blush that she could feel heating her cheeks, Castle grinned wider.

"That shade of red also suits you very nicely–"

"_Castle._"

Wisely, Castle fell silent; after more than three years as her partner, he did know when it was best to shut up. Unfortunately, that damn smirk was harder to get rid of.

After a minute or so of silence, Castle spoke again, but this time his tone was quiet, unexpectedly serious.

"You were right, though, you know."

Beckett blinked; her mind had wandered elsewhere, to places that involved Castle making her blush for very different reasons than those of just a minute ago. Clearing her throat slightly, she dragged herself back to the present, forcing herself to focus.

Letting the car slow to a stop at the red light, she glanced over at him, her gaze searching his briefly before returning to the road ahead.

"About what?"

She heard him draw a deep breath, his fingers tapping nervously on his thigh. "About what you said back there– about what you said I was."

He paused, giving her a moment to remember, to understand his meaning. _You're mine._

Then the moment passed and Castle shifted nervously in his seat, his eyes focused straight ahead.

"Well, I am."

Her heart quickened, its pace becoming slightly erratic, and she shot a glance at him, seeing the tension in his body, the stillness of his chest as he held his breath. Facing the road once more, she swallowed slightly, then forced her voice to sound light, casual, giving no hint of the extremely active butterflies that had now taken up residence in her stomach.

"What? You're an ass?"

Castle huffed a laugh, but when he turned to look at her his eyes were knowing, his smile soft.

"Yep."

Beckett gave a small nod, turning back to face the road just as the light turned green, allowing them to move forward.

It seemed like they'd been doing more and more of that lately.

Watching the road, she took a brief moment to steady herself, trying to keep her voice casual without betraying the goofy happiness that was currently warming her to her toes. Somehow, she doubted she'd succeed.

Keeping her eyes ahead, she spoke simply, her voice soft.

"Good to know."

With that, they fell into a comfortable silence, the remainder of the short trip passing without another word spoken, both of them keeping their thoughts to themselves.

And yet, somehow, neither could quite hide their smiles.

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><p><em>Hope you enjoyed it, and as always, thanks for reading!<em>


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